1. The relationship between regional blood flow in the optic nerve and the retina and the axoplasmic transport of labelled compounds in the nerve will be studied in monkeys. 2. An analysis will be made of the mechanism of action of EGTA on the outflow resistance in monkeys. 3. Isolated blood perfused cat eyes will be used to study the exchange of substances between blood and the retina. 4. Further studies will be made on the vasomotor control exerted in the eye by nerve fibres running in the oculomotor nerve.